An object weighs $m_1$ in a liquid of density $d_1$ and that in liquid of density $d_2$ is $m_2$. The density $d$ of the object is

Two liquids of densities ${\rho }_1$ and ${\rho }_2\left({\rho }_2=2{\rho }_1\right)$ are filled up behind a square wall of side $10 \mathrm{m}$ as shown in figure. Each liquid has a height of $5 \mathrm{m}$. The ratio of the forces due to these liquids exerted on upper part $MN$ to that at the lower part $NO$ is (assume that the liquids are not mixing)

Water flows in a horizontal tube (see figure). The pressure of water changes by $700 \mathrm{N} {\mathrm{m}}^{-2}$ between $A$ and $B$, where the area of cross-section are $40 {\mathrm{cm}}^2$ and $20 {\mathrm{cm}}^2$, respectively. Find the rate of flow of water through the tube (Take, density of water $=1000 \mathrm{kg} {\mathrm{m}}^{-3}$).